1. Field of the Invention
The present invention relates to air spring systems, and, more particularly, to a swaged assembly for constructing an air spring system.
2. Description of the Related Art
Pneumatic springs, commonly referred to as air springs, are used in numerous applications including motor vehicles. Air springs help to absorb shock loads in a vehicle as it traverses roadway undulations. Air springs can also help to maintain spacing between various components. In general, air springs typically consist of an internal pressurized fluid chamber within a flexible material, a rubber sleeve or bellows, which is capped at each end by a pair of end members. Usually, one end member is a piston that is movable relative to the bellows, and the other end member is an end cap, typically a bead plate that receives the pressurized air. The top bead plate is attached to the vehicle chassis. The piston is attached to the vehicle suspension system usually through a mounting stud that extends through the piston to a trailing arm.
Depending on the application, air springs can assume various configurations. Air springs can be generally categorized as either convoluted air springs or rolling lobe air springs. Convoluted air springs can have a single, double, or triple convolution. Typically, convoluted air springs have a shorter stroke, a greater spring rate and a higher load bearing capacity. To reinforce the convolutions a girdle ring is wrapped around the flexible member. Typical methods of sealing the flexible member to create a pressurized cavity include the crimped design and the sleeve type design. For the crimped design, the end members, usually bead plates, are crimped around the integrally formed bead ring of the flexible material. For the sleeve type design, the end members are attached to the flexible member by using external crimp rings that are swaged.
Rolling lobe air springs allow the flexible member to roll over onto the surface of its bottom end member, typically a piston, thereby forming an inverted lobe portion. Generally, rolling lobe air springs have a longer stroke, a lower spring rate, and a lower load bearing capacity compared to convoluted springs. As in convoluted air springs, to seal off the flexible member a bead plate may be used to crimp onto a bellows, or an end member may be swaged onto the flexible member. The general formula for calculating the spring rate of a rolling lobe type air spring can be found in U.S. Pat. No. 4,629,170. Rolling lobe air springs may also be in the form of a double rolling lobe, incorporating a second lobe at the top. The lobe at the top faces upwardly and may wrap around another piston or a modified end plate.
In operation, wheel fluctuations actuate the piston, which causes compression and expansion of the fluid within the chamber, causing the bellows to compress and expand. During compression (jounce travel), the pressure of the gas within the air spring increases. During extension (rebound travel), the pressure of the gas within the air spring decreases. This compression and extension of an air spring, expressed as a function of work (w=∫F·dx), allows for control of the ride characteristics of the equipment or vehicle as it experiences road shock. Air springs are often engineered to have a specific spring rate or spring constant, thereby controlling jounce and rebound characteristics for comfort and the desired application.
For a given application, the jounce and rebound charateristics of a double rolling lobe may be favored, but incorporating a double rolling lobe may be infeasible due to various design constraints. For instance, if the there is limited spacing the clearance needed to operate a double rolling lobe may be insufficient. Further, sediment and other foreign bodies may become lodged in the upwardly facing lobe. These foreign bodies can cause a loss of resiliance in the flexible member and may ultimately lead to air spring failure.
What is needed in the art is an improved air spring system that does not incorporate the design flaws of a double rolling lobe air spring.